1. Field of the Invention
This invention relates to polyamideimides and is particularly concerned with mixed aromatic-aliphatic copolyamideimides.
2. Description of the Prior Art
Copolyamideimides which contain the residues from trimellitic anhydride and aliphatic dicarboxylic acids in the polymer chains along with an arylene radical are well known in the art. U.S. Pat. No. 3,300,420 discloses organic solvent insoluble polyamideimide reaction products from trimellitic anhydride and aryl polyisocyanates including products wherein up to about 50 mole percent of the trimellitic anhydride may be replaced by an aromatic or aliphatic dicarboxylic acid. Such products are not melt processable. U.S. Pat. No. 3,803,100 describes polyamideimides derived from trimellitic anhydride and arylene diisocyanates that are solvent soluble but infusible and up to 60 mole percent of the trimellitic anhydride may be replaced by an aromatic dicarboxylic acid. U.S. Pat. No. 3,817,926 describes organic solvent soluble polyamideimides in which the trimellitic anhydride constituent may be replaced by up to 75 mole percent of a dicarboxylic acid, inclusive of aliphatic dicarboxylic acids, and this mixture reacted with an organic diamine first, followed by a diisocyanate. The polymer obtained thereby is characterized by a low inherent viscosity, that is to say, low molecular weight which does not give rise to a polymer having good physical properties. Similarly U.S. Pat. No. 3,884,880 discloses trimellitic anhydride-aromatic diisocyanate based copolyamideimides in which up to 50 mole of the anhydride is replaced by an aliphatic dicarboxylic acid wherein the resulting soluble polymers are of low inherent viscosity. U.S. Pat. No. 3,929,691 discloses mixed copolyamideimides containing the trimellitimideamide and aromatic amide residues which are solvent soluble and spinnable but which are not melt processable.
Heretofore, a trimellitic anhydride based copolyamideimide has not been found which is characterized by the combination of organic solvent solubility, fusibility, high molecular weight, and melt processability, as for example injection moldability, all in the same polymer.
The present invention provides copolyamideimides characterized by all of the desirable properties set forth above. Specifically, their molecular weights, as measured by inherent viscosity data, are higher than those polymers disclosed in U.S. Pat. Nos. 3,817,926 and 3,884,880 as noted in Examples 11 and 12 hereinbelow, giving rise to superior polymer properties, and, additionally, they are both solvent soluble and fusible and injection moldable.